Cirith Dúath

Sauron's Dark Land of Mordor was ringed by defensive mountain ranges. The range that ran down its western side was known as Ephel Dûath, typically translated as 'Mountains of Shadow', but literally the 'fence of shadows'. These mountains protected Mordor's western flank, but within the range was a deep pass that ran through from west to east, and above that pass another, higher and more difficult. This high and narrow pass was historically known, from the name of the mountains it crossed, as Cirith Dúath, the 'cleft of shadows'.

The name Cirith Dúath was an old one, recorded as being used during the War of the Last Alliance at the end of the Second Age. At that time, Isildur had built his city of Minas Ithil to guard the western way to the passes through Ephel Dúath. As the war went on, Isildur sent his sons Aratan and Ciryon to guard the pass of Cirith Dúath and prevent any possible escape by Sauron through that route.

From their use of the old name at that time, it seems that the Gondorians had not yet become aware of a danger lurking in the steep pass. Near the crest of the pass, the monstrous spider Shelob had created a Lair, and there she would trap unwary travellers passing through the mountains. At some point¹ after the War of the Last Alliance, the Dúnedain discovered Shelob, and their name for the pass changed from Cirith Dúath, 'cleft of shadows', to Cirith Ungol, 'pass of the spider'.

Whenever the change of name took place, we know that Shelob remained in her Lair in Cirith Ungol until at least the time of the War of the Ring. During that War, she attempted to trap the Ring-bearer Frodo Baggins and his companion as they crossed over Ephel Dúath by the old pass. In that attempt she was terribly wounded, but she evidently survived. So at least for some time into the Fourth Age, she remained in her Lair, haunting the old pass that had long ago been known as Cirith Dúath.